Catalytic Iron Filter (CIF) is a filter for removal of high loads of Hydrogen Sulphide (H2S) from the foul air and is often used as a roughing filter for the first stage of a system with a carbon filter installed as a polishing unit. It essentially protects and limits the load to the polishing media thereby extending the life span of the media and reducing operational costs.
Advantages of the CIF stage are that no chemicals are required, low water consumption and improved performance at the second stage.
They often have a small footprint and can be installed outdoors.
The foul inlet air is first passed through a small humidifier to moisten the air stream and then passes into the top of the CIF tower. The airflow through the CIF units is downward. There are two separate media beds both consisting of hydrated rusty iron pall rings. As the airflow passes through the media the hydrogen sulphide is oxidised by the iron oxide on the surface of the pall rings.
Contact time is which is normally around 12 – 15 seconds in order to achieve optimum removal efficiency. The system has two media beds to prevent the media crushing during operation, generally the top media bed will need to be changed every five years as it takes the majority of the load and both beds require changing every ten years.
The CIF unit would normally be followed by further odour treatment.